Hi there,
That sounds like a PHP Session issue. Currently our donation receipts page has some limitations. Let me explain a little:
1) When a donor is NOT a logged in user of your website it gets tricky to save information about them. We use what’s called a PHP Session cookie for that information.
2) This means that the only way that user can view that information is if they visit the page from the exact same browser with the exact same device they made the donation with. So if they made the donation on their phone, but tried to visit the donation receipt link from their desktop you’ll get that error. Same thing if they made the donation in Chrome/Desktop but tried to view it in Firefox/Desktop.
3) PHP Sessions can also be cached accidentally, so make sure that you exclude your donation receipt page from any caching you use.
Suggestions:
1) Make sure you have excluded the donation confirmation page from all types of caching you might have on your site (via plugins or your hosting).
2) You might want to consider asking your donors to create an account on your site when they donate. You can enable that per form with Give. This would allow them to view their Donation History whenever they wanted.
3) You can also customize the Donation Confirmation email to output ALL the donation data rather than just the link to the Donation Receipt page.